1. Field of the Disclosure
The present disclosure relates to a power supply system for electric vehicle and control method thereof, and more particularly to a power supply system for electric vehicle configured to select a control power for charging a low voltage battery and a control method thereof.
2. Discussion of the Related Art
The information disclosed in this Discussion of the Related Art section is only for enhancement of understanding of the general background of the present disclosure and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
In recent years, with the aim of reducing CO2 discharge in an attempt to prevent global warming and air pollution, hybrid electric vehicles (HEVs) that are provided with a secondary battery and that use both an engine and a motor as a power source, have become increasingly popular, and electric vehicles (EVs) that are provided with a secondary battery and that emit no exhaust gas are also starting to receive attention, where an electric motor is driven by electricity to operate the EV, and the battery supplies electricity to the electric motor. Generally, EVs refer to those which utilize electricity for power to a large extent, and typical EVs include an HEV (Hybrid Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle), and an EV (Electric Vehicle).
Generally, a power system of an EV includes a main battery (high voltage battery) supplying a driving power to a driving motor, a BMS (Battery Management System), a sub-battery (low voltage battery) providing a driving power to other vehicular electronic equipment and a host of electric devices.
An inverter may act as an intermediary between battery and electric motor. That is, an inverter converts a high DC (direct current) voltage generated by the main battery (high voltage battery) to an AC (alternating current) signal to control a motor. A low voltage DC-DC Converter (LDC) converts electric power of a high voltage battery into a direct current. That is, the LDC switches a direct current to an alternating current, boosts or drops the alternating current using coil, transformer, capacitance, etc., rectifies the resulting alternating current to a direct current and supplies electricity suitable for voltages used in respective electrical loads. In further details, the LDC converts the high voltage generated by the main battery (high voltage battery) to a low voltage, and outputs the low voltage to charge the sub-battery (low voltage battery).
An alternator mounted on a conventional engine vehicle serves to generate a predetermined voltage using an engine power and supply the voltage to each electric load on the vehicle and simultaneously supply a charged voltage to a battery.
Meanwhile, driving powers for motor and other electronic equipment of an EV are provided by the main battery, which is a main power of the EVs. It takes long hours to charge the main battery and a running distance of an EV by one time of charging is limited, such that many efforts are being waged to reduce the power consumption of the EV.
In an electric vehicle, the charging voltage for sub-battery is supplied from the main battery through the LDC. That is, the LDC continuously supplies a high voltage to the main battery, which is then converted to a low voltage to the sub-battery as a charging voltage. As a result, there is created a problem of continuously consuming the power of the main battery for charging the sub-battery. In addition, since the life span of the sub-battery is relatively short, it becomes necessary to replace a plurality of batteries while using the EV. Naturally, this results in additional costs over time.